You can view a list of computers which have not been polled for a specified period of time (for example, for two weeks). To do this, select the "Data - Relevance of Data" item on the main menu.
Select a necessary number of days and click the "Show" button.
After doing this, the list of outdated computers will be shown (including the computers which have never been polled). You can save this report to a file by clicking the "Save..." button.